The invention relates to a flexible enclosure for a speaker. The enclosure acts on the rear wave emanating from the speaker in two ways simultaneously. Above a xe2x80x9ctransition frequencyxe2x80x9d it acts as a baffle to dissipate acoustic energy which would otherwise cancel the front wave. Below the xe2x80x9ctransition frequencyxe2x80x9d it acts as a lens to invert the phase of the rear wave and pass it to the listening environment as reinforcement to the front wave. The result is increased bass response.
A speaker driver in open air (with no baffle) produces a front wave, and a rear wave which are 180 degrees out of phase with each other. This is because as the diaphragm of the speaker moves forward to create a compression in front it also makes a rarefaction in back. Similarly when it moves backwards it makes a compression in the rear but a rarifation in the front. In either case the sounds emanating from the front and rear are out of phase.
Without any form of baffle the sound from the rear and the front tend to commingle in the listening environment with detrimental results as they cancel each other.
To prevent this cancellation effect speaker enclosures have been developed which are usually of two types. The sealed enclosure (or infinite baffle) which is designed to prevent the rear wave from entering the listening environment, and the ported (or base reflex) enclosure which, in the best implementations permits the rear wave to enter the listening environment in phase with the front wave.
The Tuned Elastic Enclosure simultaneously acts as both a sealed enclosure above a tuneable xe2x80x9ctransition frequencyxe2x80x9d and a well designed ported enclosure below that frequency.
U.S. Pat. No. 3,812,301, issued to Lahti discloses a spherical speaker that has a cone speaker mounted within a spherical flexible sealed enclosure. The speaker diaphragm is loaded by the action of an inverted horn and the action of the enclosed air space behind the enclosure. The flexibility of the enclosure enhances the effects of the loading and it has been found that the current utilization of both loading expedients results in a response from the speaker which extends 25 Hz and an enhanced response in the frequency of 80-300 Hz. The spherical enclosure is made of flexible plastic in the thickness range of 0.040 to 0.090. The disclosed speaker has no baffle effect.
U.S. Pat. No. 5,170,436 to Powell discloses an acoustic speaker having a tuned port in the speaker enclosure. A duct extends through the tuned port into the interior of the cabinet. Reed baffles provided in the enclosure cause the entire cabinet to vibrate in the base range. This allows a small woofer to be used with the cabinet.
It is an object of the invention to provide a speaker system comprising a speaker (driver) and enclosure, that uses the back wave to enhance bass response.
It is another object of the invention to provide a speaker enclosure that uses the back wave below a transition frequency before passing it to the listening environment to enhance bass response and dissipates the back wave above the transition frequency.
It is yet another object of the invention to provide a speaker system that is inexpensive and produces superior sound.
These and other objects of the invention will be evident to one of ordinary skill in the art after reading the following disclosure of the invention.
The enclosure of the invention enables the speaker (driver) to provide greater response in the bass range by correcting the phase of the low frequency rear wave present within the enclosure, then passing it to the listening environment in correct phase to reinforce the front wave.
Below the transition frequency, the enclosure is flexible and is able to act in a manner analogous to a lens, inverting the phase of the rear wave generated within the enclosure before passing it to the listening environment. Above the transition frequency the enclosure acts as a baffle, dissipating the out of phase mid and high frequency rear wave, not permitting it to enter the listening environment. The result is greater bass response.
With the Tuned Elastic Enclosure, an underdamped speaker cone, driven by a smaller, less expensive magnet can be used, than would otherwise be conventional for similar bass output. The enclosure itself is of simple construction and the result is a low cost speaker that delivers greater bass response.